The invention relates to an apparatus for sorting lightweight, flat material such as paper sheets or plastic films. The invention also relates to a method for sorting lightweight, flat material such as paper sheets or plastic films.
From German Utility Model 94 17 627 a system and method for sorting lightweight, flat material such as paper sheets or plastic films are known in which a stream of material to be sorted is fed to an inclined sorting track constituted by a portion of a circulating, air permeable conveyor member under which a vacuum is generated and maintained. Under influence of the vacuum, flat material, such as paper and plastic film material, adheres to the conveyor member and are entrained from the drop zone to the upper end of the sorting track. Other material which is less susceptible to be held by suction through the air permeable belt, such as bottles, cans and other not generally flat material, does not adhere to the sorting track belt and descends to the lower end of the sorting track. Thus, flat material such as paper and plastic film material is sorted out of the stream of waste material.
Such a sorting step is of particular use in situations in which dry waste consisting mainly of paper, metal and plastic waste is collected in combination for efficient collection of waste. The flat material generally consists mainly of paper and the plastic film material can be sorted out of the paper in a separate sorting step, for instance employing an apparatus as disclosed in European patent application 1 970 130.
However, a problem of a sorting apparatus and method is that some non-flat material is nevertheless entrained to the upper end of the sorting track, in particular if waste is supplied at a high rate or irregularly so that high peak rates occur. This problem can to a large extent be avoided by avoiding high waste supply rates, but this entails a reduced sorting capacity.